1. Field of the Invention
The present invention relates to a positioning device and, more particularly, to a positioning device for a rod.
2. Description of the Related Art
A conventional positioning device in accordance with the prior art shown in FIG. 1 is mounted on a rod 520 and comprises a clamping ring 500 and a bolt 510. The clamping ring 500 includes a C-shaped annular wall 501, two spaced fixing plates 502 mounted on two opposite ends of the annular wall 501, and a slit 503 defined between the fixing plates 502. The clamping ring 500 is mounted on the rod 520. Then, the bolt 510 is screwed through the fixing plates 502. When the bolt 510 is screwed tightly to reduce the width of the slit 503, the annular wall 501 of the clamping ring 500 presses the rod 520 so that the rod 520 is locked. When the bolt 510 is unscrewed to enlarge the width of the slit 503, the annular wall 501 of the clamping ring 500 releases the rod 520 so that the rod 520 is unlocked. However, the user has to screw the bolt 510 for locking the rod 520 and to unscrew the bolt 510 for unlocking the rod 520, thereby wasting the time and energy. In addition, the annular wall 501 of the clamping ring 500 easily produces an elastic fatigue during a long-term utilization so that the annular wall 501 of the clamping ring 500 cannot position the rod 520 exactly and closely. Further, the conventional positioning device is not assembled conveniently.